A heating apparatus that utilizes induction heating (eddy current) has been proposed as an apparatus for heating water (see, for example, PTD 1). The eddy current heating apparatus described in PTD 1 includes a rotatable rotor having a permanent magnet disposed on an outer periphery thereof, and a heating portion made of a conductive material, which is fixed to the outside of the rotor, and in which a flow passage is formed to allow water to circulate inside. When the rotor rotates, magnetic lines of force (magnetic flux) generated by the permanent magnet around the outer periphery of the rotor move by penetrating through the heating portion, which causes eddy current to be generated in the heating portion, to heat the heating portion itself. Consequently, heat generated in the heating portion is transferred to the water circulating in the inside flow passage to heat the water.
A primary object of the above-described technology is to supply hot water by utilizing energy such as wind power or the like, and in recent years, power generation systems that similarly utilize renewable forms of energy such as wind power, hydraulic power, wave power, and the like have been attracting attention.
NPDs 1 to 3, for example, describe technologies relating to wind power generation. Wind power generation generates electric power by driving a power generator by rotating a wind turbine with winds, and converts wind energy into rotational energy to obtain the converted energy as electrical energy. Wind power generation systems generally have a structure in which a nacelle is set up on the top of a tower, and a horizontal-axis wind turbine (a wind turbine whose rotation shaft is substantially parallel to the direction of winds) is attached to the nacelle. The nacelle houses a speed-increasing machine that outputs an increased rotational speed of the rotation shaft of the wind turbine, and a power generator that is driven by the output from the speed-increasing machine. The speed-increasing machine can increase the rotational speed of the wind turbine up to a rotational speed of the power generator (1:100, for example), and incorporates a gearbox.
In recent years, there is a tendency to increase the size of wind turbines (wind power generation systems) to reduce power generation costs, and wind power generation systems of a class having a wind turbine diameter of 120 m or greater and an output per turbine of 5 MW have been put into practical use. Many of such large wind power generation systems are constructed on the ocean, for reasons of construction owing to their huge size and heavy weight.
Moreover, in wind power generation, since the power generation output (amount of power generation) varies with varying wind power, a power storage system is set up together with the wind power generation system to store unstable electric power in storage batteries, so as to smooth out the output.